The invention relates to an internal frame for a flexible kayak hull, and, particularly, a frame section having increased resistance to bending moments in a pitch direction while being laterally stable. While not limited thereto, these kayaks are designed for whitewater conditions, and so that some amount of flexure is inherent in the kayak structure for impact against rocks, boulders, and the like. However, lightweight frame sections are required in the bow and stern of the hull for proper performance. If the frame section is too heavy, the bow or stern becomes too heavy and the kayak looses its responsiveness. That is, due to the weight, for example in the bow, the kayak does not steer or turn quickly, making it hard to maneuver in whitewater.
Internal framework has been provided before in kayaks having flexible hull skins such as in U.S. Pat. No. 4,227,272 wherein a molded bow and stern frame section is disclosed; and in U.S. Pat. No. 4,407,216, both of which are issued to the same inventor herein. It has also been known to construct internal framework for flexible kayak hulls by forming the frame sections from solid resilient foam blocks.
The problem arises that as kayak hulls have developed, they have become more shallow for higher speed and peformance. The height of the hull has decreased resulting in a decrease in the height of the internal frame sections in the bow and stern of the hull. This decreased height of the frame sections has resulted in lightweight frame sections of insufficient strength to withstand bending moments in the pitch direction encountered under severe whitewater and other conditions of high dynamic stress. Using heavier, more dense materials may not be acceptable due to the weight limitations for performance.
Accordingly, an object of the present invention is to provide an internal frame section for the hull of a kayak constructed from a flexible skin enclosure.
Another object of the present invention is to provide a frame section for a flexible kayak hull having increased resistance to bending moments in a pitch direction yet which is sufficiently light weight as not to influence the performance of the kayak.
Another object of the invention is to provide an internal frame section for a flexible hull enclosure of a kayak, and the like, having increased resistance to bending moments in a pitch direction yet which is light weight and resists buckling in a lateral direction.
Another important object of the present invention is to provide an internal frame section for a flexible kayak hull which is constructed as a thin web stiffening member which effectively resists bending moments in a pitch direction, having block foam material laminated on each side to prevent buckling or warping in a lateral direction.